This invention relates generally to devices for covering growing plants to protect them from the elements, and in particular to a freestanding, insulated cover constructed from corrugated plastic for use in cultivated agricultural fields and farmlands.
Various items have been used to protect plants during their initial stages of growth in the early spring, or from harsh temperatures and frost in the autumn.
Seedlings, bulbs, and shoots are generally started in a greenhouse. Their growing environment may therein be controlled and they are protected from the elements until they reach a size to withstand the weather of early spring or the risk of adverse weather has passed, although this adds considerably to the end cost of the plant, produce, fruit, or blossoms. Plants which are particularly vulnerable to the elements-such as rose bushes or tomatoes-may often be covered with straw, burlap, or leaves in anticipation of frost or snow. Smudge pots are used in the fall to heat orchards where the trees are too large to be covered.
Styrofoam containers ranging from cup to bushel-basket size may be used as plant protectors. Small plants may also be covered with overturned potting containers, baskets, or commercially produced plant covers. Such items tend to be relatively expensive when compared to the end price which may be obtained for the plant or its produce, and it is therefore necessary that the cost of the plant protector be spread over a useful life of many growing seasons, and not add in other ways to the costs of raising those plants.
One product which has been primarily marketed to home gardeners under the trademark "Hot Caps" consists of a dome-like structure molded out of a material similar to wax impregnated paperboard. While inexpensive, this product is still degraded by the elements, and will generally withstand use for only a single season. It is difficult to anchor this product to the ground so that it will not be blown away. Furthermore, this product does not provide any ventilation for the growing plant. Although a user could cut the top off the dome or puncture holes in the side, such measures would prevent the structure from later providing the needed protection for the plant, and present a problem when the plants eventually mature and grow through those holes, then becoming too large to remove. The other available alternative is to set out and retrieve each hot cap daily, a process both impractical and expensive when dealing with a large expanse of agricultural field containing many thousands of plants.
Another device has been shown and described in U.S. Pat. No. 4,267,655 entitled "Double Walled Thermal Protective Coverings." One embodiment of this device has been marketed under the trademark "Wall-O-Water," and is intended for use primarily in the spring to accelerate the normal planting and growing season. This device comprises a plurality of tubes manufactured from a thin, flexible plastic sheeting and fastened together longitudinally. Because the plastic is very thin, rigidity is imparted to the structure by filling each individual tube with water. The tubes may be oriented in either a vertical or horizontal configuration to form side walls of a cylinder or truncated cone which surround the growing plant.
Although this device has proven effective for lengthening the early growing season, as well as accumulating and utilizing solar energy, it does present several drawbacks. Filling each tube with water is a time consuming and tedious process which requires a great deal of stooping or bending over. A water tank having the appropriate nozzle must be driven through the field, and the individual setting up the plant protectors must walk through the field or dismount the vehicle repeatedly.
It is difficult to set up the device and fill the individual tubes because they tend to collapse unless supported by some preexisting frame or structure, and the device may thereby damage delicate plants if handled improperly. Filling each tube alternately with increasing amounts of water to prevent such a collapse proves to be an even more time consuming process. Because the tubes must be individually filled with water and later emptied, and the water is expected to freeze and expand, no provision is made for the tubes to be completely sealed, and enough water may evaporate from the tubes over a short period to weaken the structure.
The only embodiment of the device which permits both ventilation and protection incorporates a drawstring threaded through loops at the top of the tubes. To use this drawstring, however, the tubes must be only partially filled with water. This eliminates any structural integrity which would otherwise hold the top of the cylinder open, and the tubes are free to fold over and close off the opening, thereby preventing any ventilation. Other embodiments of the device prevent ventilation or sunshine from reaching the plant, do not serve to protect the plant from heavy rains, hail, or wind, and require separate internal structures to protect the plant from being crushed by the water filled tubes themselves.
While the tubular plant protector permits an enclosed volume as much as four times greater than the hot caps, and indeed requires such a larger volume to permit the extended growth period which it may ostensibly provide, all the embodiments of the water filled tube design have a limiting maximum size or height above which the structure will crimp and collapse from its own weight.
A water filled plant protector also presents some unique disadvantages in the autumn, when the water increases the liklihood of frost subliming on the leaves of the plant, and retains the nighttime cold when there is no morning sunshine the subsequent day. Additionally, the water which remains trapped in each tube after being emptied keeps the devices from being stored away without drying, itself a difficult process, or leads to mold or mildew if stored improperly.
Although the plastic tubes do permit a longer useful life than the previously mentioned hot caps, they are still only expected to survive a few years of use if they are handled with the utmost of care, and not exposed to the many sharp objects one normally encounters in the field. An inadvertent scrape or blow to the water filled tubes will cause them to tear, and may result in the entire structure collapsing onto the plant. If a protector is damaged, a new protector must be obtained and filled, or a supply of extra protectors and a watering can must be carried each time one goes into the field.